Modern wind turbines have rotor blades rotatably mounted on a rotor, it being possible to vary an angle of incidence of the wind through an individual change of the blade angle relative for each rotor blade. The change takes place through a pitch drive which is connected to an external mains supply and has a controllable electric motor, to which, as well as to a converter, control and regulating devices are assigned for adjusting the rotor blade, which are arranged in an electrical switchgear cabinet (pitch switchgear cabinet). Essential components of a pitch switchgear cabinet are electronic converter units for the controlled drive of the pitch system. Such a cabinet is thus also designated as a converter box. A converter box has e.g. electrical or electronic components and equipment such as e.g. mains adapters, circuit breakers and plugs, input/output units, fuses, transformers and other parts and equipment, which are also provided in a classic switchgear cabinet for an electrical drive.
An individual pitch drive with an associated control cabinet is usually assigned to each blade (axis), so that a plurality of pitch switchgear cabinets are provided in a wind turbine (WEA) which are usually arranged on the upper masthead (top box) of the turbine and configured as a compact box sealed with a cover. They are arranged there either in the rotating part (hub) and/or in the fixed part of the turbine (gondola), being preferably arranged, however, close to the support of the rotor blade in the hub. If the control of the pitch system runs in a coordinated manner for a plurality of axes, what is known as a master control cabinet (control box) can additionally be provided in the hub or also in the gondola, which is interconnected to the associated axis boxes.
Due to the installation site and the mounting location, these boxes are exposed to particularly extreme weather conditions.
In the event of power interruptions or power failure it must be ensured that the voltage supply of the pitch drive is maintained at least for a short time. Each pitch drive therefore also has additional direct voltage sources arranged in the rotor or in the gondola in the form of accumulators or rechargeable capacitors, which are directly connected to the respective drive unit (converter+motor). This voltage source ensures that in the event of failure of the mains supply, the energy supply of the pitch drive is maintained at least for a certain time. Through an actuation of the motor, the respective rotor blade is brought into what is known as the feathering position or parking position and the turbine thus shuts down or operates further only with secure rotary speed (Fail Safe Function). Due to the mounting location, the rechargeable direct voltage sources with the associated switches are also enclosed in a box-shaped cabinet (accumulator box), which is usually arranged close to the associated axis box.
Converter box and accumulator box thus form a switchgear cabinet combination of two or a plurality of cabinets or boxes which are directly connected to each other or are adjacently arranged.
A wind turbine with three rotor blades can have up to 7 switchgear cabinets which are constructed differently according to requirements and function and must each be made individually. The different switchgear cabinets are today also constructed in a modular manner to an extent, i.e. the individual components are assembled according to their function and each form either an individual module or segment or the arrangement has a plurality of module housings which are mechanically and electrically connected to each other.
A DE patent application of the applicant not yet published on the priority date having the publication number DE 10 2009 044 034 A1 shows a wind turbine with an electrical switchgear cabinet arrangement in which a circuit for actuating at least one blade adjustment drive (pitch system) is provided by means of which one or a plurality of rotor blades of the wind turbine can be rotated about their blade axes. The switchgear cabinet arrangement has a plurality of modules which are assembled in one compact and radially central container, the inner space of which is divided into a plurality of segments (modules) in particular by partitions. The partitions form a switchgear cabinet or module with the wall of a segment, to which switchgear cabinet or module a certain function is assigned.
Thus a module is provided for the function of the accumulator cabinet, another module for the function of the converter cabinet, a further module for the function of the control cabinet and optionally further modules for other functions. The individual modules can each form a separate structural unit which can also be made separately. However, the above-mentioned special electrical function is assigned to each module or honeycomb. Interchangeability between the functions is not provided for with the individual modules.
Switchgear cabinets constructed in a modular manner are known from the general switchgear cabinet structure (e.g. DE 102 41 574 B4) which have a plurality of module housings and are connected to each other via a connection element. The module housings can each have a series of electrical plug connections which are either led outwardly or are provided for connecting the module housings.
A switchgear cabinet with a switchgear cabinet box having a plurality of modules fixed to a support rail is known from DE 197 43 974 A1, a certain function being assigned to each individual module. The switchgear cabinet is only function-block orientated and modularly constructed. The modules do not differ in their technical function from a classic switchgear cabinet, rather only in their simpler mode of installation and/or upgrading.
The substantial disadvantage of the known solutions is that with an increasing number of electrical components, caused by technical changes to the wind turbine, the layout of the switchgear cabinet must be enlarged. A further cabinet or a module must be added to the existing switchgear cabinet arrangement if necessary. If a higher level of equipping is required, e.g. if the additional or larger components are required, a new cabinet is designed or an additional housing module is added to the existing arrangement.
With identical parts or identical functions of switchgear cabinets, the turbine operator therefore always has to design and make new switchgear cabinets with the corresponding content for altered technical requirements, which switchgear cabinets have be produced individually, held in stock and have to each be fitted. This makes switchgear cabinet production expensive and laborious.
Since there is limited space available in the current hubs of wind turbines, the optimal balance between necessary space for electrical components and the size of the hub has to be established. It is not unusual that axis cabinets in particular cannot once again be removed following installation in the hub without the blades of the WEA having to be dismounted. In the small space conditions in the hub, this involves significant effort or is usually not possible. In the case of a complete failure of a pitch system, the hub, including the blades, usually has to be removed from the gondola. The blades are then dismounted on the ground in order to remove the axis switchgear cabinets through the blade bearing openings and to optionally install new switchgear cabinets or modules.